//! The primitive widget used for displaying text.

use {Color, Colorable, FontSize, Ui, Widget};
use position::{Dimension, Scalar};
use std;
use text;
use utils;
use widget;


/// Displays some given text centered within a rectangular area.
///
/// By default, the rectangular dimensions are fit to the area occuppied by the text.
///
/// If some horizontal dimension is given, the text will automatically wrap to the width and align
/// in accordance with the produced **Alignment**.
#[derive(Clone, Debug, WidgetCommon_)]
pub struct Text<'a> {
    /// Data necessary and common for all widget builder types.
    #[conrod(common_builder)]
    pub common: widget::CommonBuilder,
    /// The text to be drawn by the **Text**.
    pub text: &'a str,
    /// Unique styling for the **Text**.
    pub style: Style,
}

/// The styling for a **Text**'s graphics.
#[derive(Copy, Clone, Debug, Default, PartialEq, WidgetStyle_)]
pub struct Style {
    /// The font size for the **Text**.
    #[conrod(default = "theme.font_size_medium")]
    pub font_size: Option<FontSize>,
    /// The color of the **Text**.
    #[conrod(default = "theme.label_color")]
    pub color: Option<Color>,
    /// Whether or not the text should wrap around the width.
    #[conrod(default = "Some(Wrap::Whitespace)")]
    pub maybe_wrap: Option<Option<Wrap>>,
    /// The spacing between consecutive lines.
    #[conrod(default = "1.0")]
    pub line_spacing: Option<Scalar>,
    /// Alignment of the text along the *x* axis.
    #[conrod(default = "text::Justify::Left")]
    pub justify: Option<text::Justify>,
    /// The id of the font to use for rendering and layout.
    #[conrod(default = "theme.font_id")]
    pub font_id: Option<Option<text::font::Id>>,
    // /// The line styling for the text.
    // #[conrod(default = "None")]
    // pub line: Option<Option<Line>>,
}

/// The way in which text should wrap around the width.
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum Wrap {
    /// Wrap at the first character that exceeds the width.
    Character,
    /// Wrap at the first word that exceeds the width.
    Whitespace,
}

// /// Line styling for the **Text**.
// pub enum Line {
//     /// Underline the text.
//     Under,
//     /// Overline the text.
//     Over,
//     /// Strikethrough the text.
//     Through,
// }

/// The state to be stored between updates for the **Text**.
#[derive(Clone, Debug, PartialEq)]
pub struct State {
    /// An owned version of the string.
    pub string: String,
    /// The indices and width for each line of text within the `string`.
    pub line_infos: Vec<text::line::Info>,
}


impl<'a> Text<'a> {

    /// Build a new **Text** widget.
    pub fn new(text: &'a str) -> Self {
        Text {
            common: widget::CommonBuilder::default(),
            text: text,
            style: Style::default(),
        }
    }

    /// Specify that the **Text** should not wrap lines around the width.
    pub fn no_line_wrap(mut self) -> Self {
        self.style.maybe_wrap = Some(None);
        self
    }

    /// Line wrap the **Text** at the beginning of the first word that exceeds the width.
    pub fn wrap_by_word(mut self) -> Self {
        self.style.maybe_wrap = Some(Some(Wrap::Whitespace));
        self
    }

    /// Line wrap the **Text** at the beginning of the first character that exceeds the width.
    pub fn wrap_by_character(mut self) -> Self {
        self.style.maybe_wrap = Some(Some(Wrap::Character));
        self
    }

    /// A method for specifying the `Font` used for displaying the `Text`.
    pub fn font_id(mut self, font_id: text::font::Id) -> Self {
        self.style.font_id =  Some(Some(font_id));
        self
    }

    /// Build the **Text** with the given **Style**.
    pub fn with_style(mut self, style: Style) -> Self {
        self.style = style;
        self
    }

    /// Align the text to the left of its bounding **Rect**'s *x* axis range.
    pub fn left_justify(self) -> Self {
        self.justify(text::Justify::Left)
    }

    /// Align the text to the middle of its bounding **Rect**'s *x* axis range.
    pub fn center_justify(self) -> Self {
        self.justify(text::Justify::Center)
    }

    /// Align the text to the right of its bounding **Rect**'s *x* axis range.
    pub fn right_justify(self) -> Self {
        self.justify(text::Justify::Right)
    }

    builder_methods!{
        pub font_size { style.font_size = Some(FontSize) }
        pub justify { style.justify = Some(text::Justify) }
        pub line_spacing { style.line_spacing = Some(Scalar) }
    }

}


impl<'a> Widget for Text<'a> {
    type State = State;
    type Style = Style;
    type Event = ();

    fn init_state(&self, _: widget::id::Generator) -> Self::State {
        State {
            string: String::new(),
            line_infos: Vec::new(),
        }
    }

    fn style(&self) -> Self::Style {
        self.style.clone()
    }

    /// If no specific width was given, we'll use the width of the widest line as a default.
    ///
    /// The `Font` used by the `Text` is retrieved in order to determine the width of each line. If
    /// the font used by the `Text` cannot be found, a dimension of `Absolute(0.0)` is returned.
    fn default_x_dimension(&self, ui: &Ui) -> Dimension {
        let font = match self.style.font_id(&ui.theme)
            .or(ui.fonts.ids().next())
            .and_then(|id| ui.fonts.get(id))
        {
            Some(font) => font,
            None => return Dimension::Absolute(0.0),
        };

        let font_size = self.style.font_size(&ui.theme);
        let mut max_width = 0.0;
        for line in self.text.lines() {
            let width = text::line::width(line, font, font_size);
            max_width = utils::partial_max(max_width, width);
        }
        Dimension::Absolute(max_width)
    }

    /// If no specific height was given, we'll use the total height of the text as a default.
    ///
    /// The `Font` used by the `Text` is retrieved in order to determine the width of each line. If
    /// the font used by the `Text` cannot be found, a dimension of `Absolute(0.0)` is returned.
    fn default_y_dimension(&self, ui: &Ui) -> Dimension {
        use position::Sizeable;

        let font = match self.style.font_id(&ui.theme)
            .or(ui.fonts.ids().next())
            .and_then(|id| ui.fonts.get(id))
        {
            Some(font) => font,
            None => return Dimension::Absolute(0.0),
        };

        let text = &self.text;
        let font_size = self.style.font_size(&ui.theme);
        let num_lines = match self.style.maybe_wrap(&ui.theme) {
            None => text.lines().count(),
            Some(wrap) => match self.get_w(ui) {
                None => text.lines().count(),
                Some(max_w) => match wrap {
                    Wrap::Character =>
                        text::line::infos(text, font, font_size)
                            .wrap_by_character(max_w)
                            .count(),
                    Wrap::Whitespace =>
                        text::line::infos(text, font, font_size)
                            .wrap_by_whitespace(max_w)
                            .count(),
                },
            },
        };
        let line_spacing = self.style.line_spacing(&ui.theme);
        let height = text::height(std::cmp::max(num_lines, 1), font_size, line_spacing);
        Dimension::Absolute(height)
    }

    /// Update the state of the Text.
    fn update(self, args: widget::UpdateArgs<Self>) -> Self::Event {
        let widget::UpdateArgs { rect, state, style, ui, .. } = args;
        let Text { text, .. } = self;

        let maybe_wrap = style.maybe_wrap(ui.theme());
        let font_size = style.font_size(ui.theme());

        let font = match style.font_id(&ui.theme)
            .or(ui.fonts.ids().next())
            .and_then(|id| ui.fonts.get(id))
        {
            Some(font) => font,
            None => return,
        };

        // Produces an iterator yielding info for each line within the `text`.
        let new_line_infos = || match maybe_wrap {
            None =>
                text::line::infos(text, font, font_size),
            Some(Wrap::Character) =>
                text::line::infos(text, font, font_size).wrap_by_character(rect.w()),
            Some(Wrap::Whitespace) =>
                text::line::infos(text, font, font_size).wrap_by_whitespace(rect.w()),
        };

        // If the string is different, we must update both the string and the line breaks.
        if &state.string[..] != text {
            state.update(|state| {
                state.string = text.to_owned();
                state.line_infos = new_line_infos().collect();
            });

        // Otherwise, we'll check to see if we have to update the line breaks.
        } else {
            use utils::write_if_different;
            use std::borrow::Cow;

            // Compare the line_infos and only collect the new ones if they are different.
            let maybe_new_line_infos = {
                let line_infos = &state.line_infos[..];
                match write_if_different(line_infos, new_line_infos()) {
                    Cow::Owned(new) => Some(new),
                    _ => None,
                }
            };

            if let Some(new_line_infos) = maybe_new_line_infos {
                state.update(|state| state.line_infos = new_line_infos);
            }
        }
    }

}

impl<'a> Colorable for Text<'a> {
    fn color(mut self, color: Color) -> Self {
        self.style.color = Some(color);
        self
    }
}